Pollution is one of the most serious public health problems in cities around the world. Various pollutants or containments in air or water may affect the health of the general public. Therefore, the quality of air and water must be regularly examined to ensure that some poisonous or hazardous pollutants do not exceed safety levels.
The concentration of these pollutants may be determined by using testing agents. The traditional chemical testing approaches are time consuming and may not response promptly. Alternatively, material characterization techniques in laboratories may be used to analyse the concentration of a target substance and even the composition of a testing sample. Although the results may be very accurate and sensitive, these techniques used in laboratories may not be suitable for daily applications which may requires prompt and low-cost testing results.